[Simh] Booting the vax750 simulator.

[Ethan Dicks]

On Mon, Jul 6, 2015 at 3:41 PM, Mark Pizzolato - Info Comm
<Mark at infocomm.com> wrote:
> Hi Mattis,
>
> I’m working with the disk image you provided.  I see the failure on the
> VAX750 simulator.
> Have you tried earlier versions of Ultrix on the 750 simulator?
>
> I initially look at the crash message:
>
> sim> b rq0

In a similar vein, some months ago, I was trying to find why that
wouldn't boot 4.3BSD on a Simh 11/730 RB730 disk and I got as far as
tracing into BSD's driver rb.c since it was very early in the process
that things went sideways.  I wouldn't be surprised if these two UNIX
boot failures were related - differences/assumptions in how drivers
will treat controllers in VMS that don't apply to UNIX.

> machine check 2: non-existant reference error
>        sumpar  = 2
>         va      = 80001a90
>         pc      = 80087c61
>
> I note that the PC mentioned is: 80087c61.
>
> If I do the following:
>
>      sim> BRE 80087c61>
>      sim> SET CPU HISTORY=300
>      sim> B RQ0
>
> Execution flows up to the indicated address and if I single step from there,
> the exception is taken.

I at least had (still have) the source for 4.3BSD.  I did narrow
things down quite a bit, but then I ran off to learn more about how
the disk controller works and haven't put any time into it for a few
months.

-ethan